1. Field of the Invention
The present invention relates to an ink jet recording head and manufacturing method thereof and an ink jet recording apparatus.
The present invention also relates to a discharge opening (orifice) plate and manufacturing method thereof, and an ink jet recording head with the plate, and an ink jet apparatus with the head.
2. Related Background Art
As the liquid jet recording device of this type of the prior art, there have been proposed various devices such as one in which fine droplets are discharged by generating pressure difference in the liquid channel through deformation of a piezoelectric element, one in which a pair of electrodes are provided to deflect, or one in which droplets are discharged from the discharging orifices by utilizing heat energy such as by generating abruptly heat from the heat generating element arranged in the liquid channel, thereby generating bubbles, etc.
Among them, the liquid jet recording head according to the system in which the recording liquid is discharged by utilizing heat energy is particularly attracting attention as one which is capable of recording with high resolving power because liquid discharging outlets such as orifices for formation of droplets for flying by discharging droplets for recording, etc., (hereinafter also called as "orifices") can be arranged at high density, can be made compact as a whole as the recording head, can fully utilize the recent technical progresses in the field of semiconductors as well as the advantages of IC technique and microworking technique of which improvements of reliability are marked, can be easily made lengthy and planar (dimensional), etc., whereby it can be easily made into multi-nozzle and arranged at high density, and yet productivity during bulk production is good to make the production cost lower.
FIGS. 1A and 1B are respectively a schematic exploded perspective view and a schematic perspective after bonding showing an example of the liquid jet recording head of this type of the prior art.
In these Figures, 1 is a first substrate comprising Si, etc., comprising a group of electricity-heater converters and wiring portions thereof provided as the energy generating element for generating the energy to be utilized for discharging liquid on its upper surface. 8 is a second substrate, having an introducing inlet 9 for liquid for recording such as ink (hereinafter merely called as "ink"), a groove 11A for forming an ink flow channel 11 corresponding to the electricity heat converter, an ink flow channel wall 10 and a concavity 12 which becomes the common liquid chamber for storing ink and also communicating it to the respective flow channels formed thereon.
As shown in FIG. 1A, the first and the second substrates are mutually adhered and fixed with an adhesive 13 to assemble a recording head as shown in FIG. 1B.
However, the head obtained by the method as described above has the problem that the straight forward progress of the ink droplets is impaired. This is, above all, due to the fact that the orifices, which are formed of materials of different qualities, cause difference in wettability with the ink at the peripherals of orifices. In the prior art, for the purpose of avoiding such problem, it has been proposed to prepare separately an orifice plate comprising orifices molded by etching of a metal plate or a photosensitive glass plate, or an orifice plate comprising orifices by hole working on a resin film, etc., and plastering it onto the main head.
However, in the liquid recording head with such constitution (hereinafter also called "ink jet recording head" or merely "recording head"), there ensued the following problems.
In the ink jet recording head as described above, the step of bonding an orifice plate is included during its preparation, and it is necessary to perform strict registration between the orifice and the flow channel portion during said bonding. Also, since said bonding can be done with difficulty when the end surfaces of the first and the second substrate to be bonded to the orifice plate are not coincident in a plane, difficulty can also ensue during adhesion of both substrates for this reason.
In addition, the orifice plate is also adhered by use of an adhesive, but since the pitch of the flow channel 11 and the height of the flow channel wall 10 are fine to the extent of about some 10 .mu.m, unless the coated amount (thickness) of the adhesive layer 13 is controlled to a few .mu.m, the adhesive may come out to the flow channel side because of the pressure applied during bonding, whereby there may be caused such fear that the low channel diameter or the discharging orifice diameter may be varied, even leading to clogging. Also, when the adhesive force is not sufficient, there is the fear that peeling of the orifice plate may occur.
Further, in the orifice plate formed of a resin film, because the resin film has generally a thickness of about 20 to 50 .mu.m, not only handling is cumbersome, but also it may be considered that wrinkles may be formed or bubbles may be introduced during plastering to effect improper plastering.
The complexity of the preparation steps and the large number of steps as described above bring about increase in the production cost of recording heads, and this has been also a problem in making the recording head as described above, or the recording head constituted by integration with an ink tank, etc. which is the ink supplying source disposable.
The contents as described above are to be described in more detail as follows. The ink jet recording head is constituted of an orifice plate 40 having orifices 41 as the discharging outlet, a ceiling plate 400 having ink channel grooves 401 communicated to the respective orifices, and a heater board 100 constituting a part of the ink channel and having energy generating elements 101A for generating energy to be utilized for discharging ink, as shown in FIG. 2.
Generally speaking, the orifice plate is provided for the purpose of constituting the discharging outlet surface of the same member in order to prevent slippage in the discharging direction of discharged ink droplet caused by the difference in wettability between the heater board and the ceiling plate, and also the orifice, including its shape, etc. is an important element influencing the discharging performance of the ink jet recording head. Above all, the orifice through which the ink is discharged becomes the most important portion, and with high developments of the image recording technique and the recording head production technique in recent years as described above, the orifice size (orifice diameter) has become miniaturized and a plurality of orifices have become provided at high density.
On the other hand, various contrivances have been made in the prior art for working of orifice. Some examples are mentioned below:
(1) mechanical working with drill;
(2) fine working by discharging working;
(3) fine working by anisotropic etching of Si;
(4) the method by patterning according to photolithography and plating;
(5) fine working with carbon dioxide, YAG laser, etc.
However, as described above, the recording technique at the present time demands higher precision and higher speed as a matter of course, and along with this demand, the dimension of the orifice of the ink jet recording head has been miniaturized, and the orifice density increased, and yet the head has become to have a plurality of orifices.
In such point of view, according to the methods of prior art examples (1) and (2) as mentioned above, there were involved such problems that miniaturization of orifice dimension was difficult, and also that the efficiency was not good in working of a plurality of orifices of high density.
On the other hand, in the method of (3), there was the problem that the cost of Si material for the orifice plate was high in cost, and the working time was long.
Further, in the method of (4), the preparation steps from photolithography to plating are long, and also auxiliary materials such as substrate and resist, etc. must be employed.
In addition, the method of (5) could not prepare a satisfactory orifice complying with the above demand for the reason as described below.
Working by carbon dioxide laser and YAG laser was not sufficient in laser output, and both shape and precision of the orifice formed were not satisfactory. For example, the orifice formed by YAG laser is not circular in shape, and also foreign matters not sufficiently removed by laser are attached around the orifice. Also depending on the material and the thickness of the orifice plate, it also sometimes happened that no orifice, namely an opening portion, could be formed.
Also, since working by carbon dioxide laser and YAG laser is done by working orifices one by one, it is time consuming for working of a plurality of orifices and not suitable for bulk productivity.
Further, although a plurality of orifices must be correct in each positional precision, working was more difficult, because a movable portion for enabling precise registration was also required in working by carbon dioxide laser and YAG laser of the prior art.
As described above, according to the methods of the prior art, the respective problems were involved in the above-mentioned demand, and they were not sufficiently satisfactory as the working method of orifices.
On the other hand, recording by an ink jet recording head corresponds to higher precision, higher speed as described above, and improvement of its reliability has also become important. Accordingly, improvements have been also been made to ink. As a consequence, since the material in contact with ink is demanded to have ink resistance performance, the material which becomes the orifice plate is also required to satisfy such demand. Therefore, orifice working may be sometimes difficult depending on its material.
Also, the ink jet recording head is constituted of an orifice plate, a ceiling plate and a substrate as described above. Above all, orifices and ink channels communicated thereto, when not correctly registered in their positions, will badly affect discharging performance, even causing non-discharging in the worst case.
However, since both orifices and ink channels are fine in their sizes and constituted at high densities, it is difficult to assemble with correct registration, thus posing a great problem in preparation of ink jet recording head.
The above content can be explained below from a different aspect.
As mentioned above, the main body of the ink jet recording head comprised of, for example as shown in FIG. 2, the orifice plate 40 having the orifice 41 (discharge plate), the ceiling plate for forming the ink liquid path communicated with each orifice, and the base member constituting a part of the path 401 and having the electro-mechanical converting element 101A for generating energy used for discharging the ink.
The orifice plate has a fine orifice for discharging the ink, which orifice has great significance affecting the discharge character of the ink jet recording head. In detail, it is necessary for the orifice plate of the ink jet recording head to be excellent in workability since a fine orifice is provided, and excellent in ink-proof character since it is directly contacted with the ink.
Conventionally, the metallic plate of SnS, Ni, Cr, Al, and resin film material such as polyimide (PI), polyethersulfone (PES), polyetheretherketone (PEEK). and polyester (PE) which can be formed easily in predetermined thickness and in low cost can be used.
On the other hand, the recording at high speed and very fine quality has been required in these days with the progress of the recording technique, and for this reason the orifice is formed small in diameter and with high density. Consequently, there have been adopted various kinds of working methods for the orifice, among which, one using the laser light is used for orifice forming since it is suitable for fine working.
However, it is very difficult to connect the perforated orifice plate and the corresponding ink liquid path, and positional shift or offset therebetween is generated to deteriorate the discharge quality as well as recording character. In addition, the adhesive used for connection might go into the liquid path due to positional shift.
To add further, as the ink jet recording head utilizing a discharging orifice plate, for example, those with constitutions shown in FIGS. 3A to 3C and FIGS. 4A and 4B have been known.
The recording head with the constitution shown in FIG. 3 has a constitution obtained by providing, for example, an ink channel wall 7A comprising a cured film of a photosensitive resin, etc. as shown in FIG. 3B and an outer frame 8A constituting liquid chamber, etc. on a substrate 100 comprising a glass, etc. having an energy generating member 101A for generating the energy to be utilized for discharging ink such as a heat generating element, a piezoelectric element, etc. as shown in FIG. 3A, then bonding a cover 11B for ink passages having ink feeding holes 9A thereto, further cutting the channel downstream portion of the bonded body obtained (the main recording head portion) along the line C--C to control the channel length, followed by bonding of a discharging orifice plate 40 having thru-holes for formation of discharging orifices as shown in FIG. 3C to the channel opening end surface formed by said cutting in predetermined positional relationship.
On the other hand, the recording head with the constitution shown in FIG. 4A has a constitution obtained by forming a main recording head portion provided with an ink channel wall 7A, comprising, for example, a cured resin film of a photosensitive resin, etc. and an outer frame 8A, as shown in FIG. 4B on a substrate 100 comprising a glass, etc. having an ink discharging energy generating member 101A generating energy used for discharging ink such as a heat-generating element, piezoelectric element, etc. as shown in FIG. 4A, and bonding a discharging orifice plate 12A to the upper part thereof in predetermined positional relationship.
The constitution of the discharging orifice plate for constituting the ink jet recording head with the constitution as described above and the characteristics to ink have great influences on the recording characteristics of the ink jet recording head such as the discharging direction of ink, the amount of the ink discharged, etc., and various investigations have been done in the prior art about the material to be used for formation of the discharging material and its structure.
Concerning the characteristics of the discharging plate in the prior art, the problems to be solved may include the following problems.
a) In bonding between the discharging orifice plate and the main recording head portion, it is necessary to coat an adhesive on the bonding surface on the main portion side, but it is difficult to coat the adhesive uniformly, efficiently and with good workability onto the bonding surface on the main portion side, and yet the adhesive is liable to come around into the flow channel portion, whereby the production yield is low to be poor in bulk productivity.
Further, when coating of the adhesive is carried out so that the adhesive may not flow into the flow channel, the adhesive cannot be supplied to the peripheral portion of the flow channel in most cases, and if bonding is effected under such state with the discharging orifice plate, a gap will be formed between the discharging plate and the main portion, wherein ink may be pooled to cause readily interference with stable ink discharging.
b) In the case of providing a liquid repellent (ink repellent) coating layer for obtaining good ink discharged state on the surface of the discharging orifice plate which becomes the outer wall surface when bonded to the recording head (the surface on the side where ink is discharged, hereinafter called "discharging orifice surface"), it is difficult to coat uniformly the material for liquid repellent coating layer onto said surface, and also it is difficult to inhibit flowing of the material for formation of liquid repellent coating layer to the inner surface of the discharging orifice which is demanded to be inkphillic, whereby the product yield is low to be poor in productivity.
Also, as described above, the ink jet head to be applied to the ink jet recording device is provided generally with an ink energy discharging member, ink channels, ink discharging orifices and a liquid chamber of ink.
The output according to ink jet recording device is now demanded to be higher in resolving power and speed, and as the means for solving this, improvements of pitch precision and diameter precision of discharging orifice, and further ink repellent treatment in the vicinity of discharging orifice may be mentioned. For preparation of such ink jet head, there has been employed the method in which first fine grooves are formed on a substrate such as glass, metal, plastic, etc., the substrate is bonded to an appropriate plate to form liquid channels for ink within the head, and then a discharging orifice plate having holes, pitches precisely worked by electro-forming, etching, etc. is bonded, followed by application of ink repellent treatment on the whole plate surface.
The ink jet prepared according to the method of the prior art as described above has problems in preparation during bonding of the discharging orifice plate and during ink repellent treatment. In short, during bonding of the discharging orifice plate, generally a means of coating the plate back surface or the front surface of the ink channel with an adhesive and bonding the both is employed, but during coating of the adhesive, there ensues the problem that a part or all of the ink channel or the discharging orifice portion finely worked is filled with the adhesive. Further, during ink repellent treatment, it is generally practiced to attach a fluorine type or silicon type thin film on the whole plate surface, and also at this time, the phenomenon of collapsing of hole similarly occurs as during coating of the adhesive as described above. Also, in aspect of preparation cost, there is the problem that electro-forming or etching is expensive.
To say repeatedly, an ink jet recording head having a discharging orifice plate formed with provision of thru-holes on a plate material has, for example, a representative constitution as shown in FIG. 5.
More specifically, it has a structure comprising a discharging orifice plate 40 having discharging orifices 41 communicated to the channel bonded to the opened face thereat a bonded body having a substrate 100 provided with an energy generating member 101A formed by wall member 7A for generating the energy to be utilized for discharging ink within the ink channel and a ceiling plate 11B bonded together.
The structure of the discharging orifice structure and its characteristics to ink have great influences on the recording characteristics of an ink jet recording head such as the discharging direction of ink, the droplet amount of discharged ink, etc., and various investigations have been made in the prior art about the material to be used for formation of the discharging orifice plate and its structure.
As the problem to be improved in the characteristics of the discharging orifice plate, there is the problem that when a light pool of ink is formed around the discharging orifice on the outer wall surface 40a of the discharging orifice plate, disturbance is liable to occur in the discharging direction of ink as shown in FIG. 6B, whereby no stable ink discharging can be obtained (see FIG. 6A) and no good recording can be performed.
Moreover, when an ink attached film is formed on the whole surface around the discharging orifice, scattering of ink during ink discharging (splash phenomenon) occurs, whereby no stable recording can be performed, and the amount of the ink attached around the discharging orifice is further increased to develop and enlarge the ink pool. If the ink pool is excessively enlarged, ink discharging through the discharging orifice may sometimes become impossible.
Accordingly, there has been known the method to prevent formation of such ink pool as described above onto the outer wall surface of the discharging orifice by applying water repellent treatment on the outer wall surface of the discharging orifice plate.
In the water repellent treatment of the outer wall surface, the treatment is required to be performed so that the water repellent treatment may not be extended to the inner surface of the discharging orifice which is demanded to be inkphillic.
The water repellent treatment of the outer surface of the discharging orifice in the prior art has been performed by forming a thin layer of an ink repellent surface treating agent on the surface of a transfer member and transferring the thin layer onto the surface having the discharging orifice of the ink jet recording head.
Whereas, the method of the prior art have involved such problems that the treatment working is cumbersome, and also that the water repellent agent may be progressed to the inner portion of the discharging orifice, transfer cannot be sufficiently effected or even water repellent surface can not be formed because of deterioration of the transfer member.
As described above, the ink jet recording head is generally equipped with fine ink discharging orifice, ink channel and ink discharging energy generating element provided on a part of the ink channel.
As the method for preparing such ink jet recording head, for example, there has been known the method in which fine groove is formed by cutting, etching, etc. on a substrate such as glass, metal, etc., and then the substrate having the groove formed thereon is bonded to another appropriate substrate to form an ink channel within the head.
In the case of having a plurality of ink channels, those channels are in most cases communicated to a common liquid chamber and constituted so that the recording liquid may be supplied smoothly and sufficiently into the liquid channels.
Whereas, for supplying sufficient amount of recording liquid corresponding to the amount consumed by discharging of the liquid into the liquid channels, it is desirable to have a common liquid chamber of a volume with sufficient room relative to the amount consumed. However, with a common liquid chamber having a height virtually equal to the height of the ink channel, flow resistance of the recording liquid cannot be made substantially smaller, and therefore in spite of room in volume, no sufficient supply of the recording liquid can be done in some cases.
Accordingly, it becomes the general constitution to make the height of the common liquid chamber sufficiently larger than the height of the liquid channel.
However, in the method of forming fine grooves on a substrate such as glass or metal, it is difficult to form a common liquid chamber having a sufficient height relative to the height of ink channel.
It is also possible to make the height of the common chamber greater by increasing the etching amount of the common liquid chamber by repeating etching for plural times, but this method increases the steps and therefore cannot be said to respond sufficiently to the demands for cost down or productivity.
Accordingly, it has been practiced to prepare separately the common liquid chamber portion and bond the common liquid chamber portion to the end of the ink channel portion, thereby forming a desired common liquid chamber.
According to this method, sufficient common liquid chamber volume can be obtained easily and therefore it is preferable in aspect of performance of the ink jet head.
However, the method of bonding separately parts inherently has the problems of increase of number of steps, lowering in productivity, and there remain still points to be solved for accomplishing much cost down.
Also, in the case of using such method, generation of stress or positional slippage accompanied with shrinkage by curing of the adhesive, leak of the recording liquid due to incomplete sealing, flowing of the adhesive into the liquid channel or into the common liquid chamber or clogging occurred in some cases.
In addition, as described above, the recording technique at the present time demands higher precision and higher speed as a matter of course, and according to such demands, the discharging orifices of the ink jet recording head became fine in dimension, higher in orifice density, and also became to have a plurality of orifice groups.
Particularly, for higher densification, the pitch between the recording dots becomes narrower, and for making the fluid resistance through the ink path for higher speed, there is the demand to expand the pitch between orifices.
For this purpose, by taking broad pitch between orifices and working the respective discharging orifices obliquely to form the discharging directions of the recording liquid so as to be convergent, it becomes possible to perform highly precise recording. However, according to the working method of the prior art, it has been difficult to perform working with delicate variances in the discharging angle for the respective orifices.
Also, in a recording head having a plurality of the respective orifice rows for high speed recording or color recording, if the distance between the respective orifice rows is large, great memory size is required for adjusting the Dot signals between the respective orifice rows, thereby resulting in the cost-up of the main printer.